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Failover to DR server Expand / Collapse
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Posted Wednesday, February 25, 2009 6:21 AM
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Hi

I have a question regarding failover to DR server in case of disaster. What happens to sysservers table? Does it need to be modified to add the name of DR server?
Although our application is using C-NAME to accessing database but when we had failover we were getting erros that "[replica-server-name]" is not specified in sysservers.

We have been using XoSoft replication tool for failover.

PS: We arer using SQL server 2005.

Post #664182
Posted Tuesday, April 13, 2010 10:48 AM
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This is an interesting error. You are correct that the SQL System DB's are replicated by CA XOSoft, which would include the SYSSERVERS table within the MASTER database. The error you are recieving is referencing the SRVID field and the Severname for the same record. This is most likely the reesult of an RPC call referencing SRVID = 0 in the SYSSERVERS table which is then referencing the wrong server name. You can manually add the record to the DB using the SP_ADDSERVER stored procedure. Add the servername of the Replica server.

You mention that you're using CNAMES. a CNAME would point to an A record in DNS. CA XOsoft modifies the A record of the Master Server when Redirect DNS is configured. I suspect this may be part of the issue as well. I would properly configure my applications and clients to connect to the A record. IT is not necessarily required but it causes less confusion in the long run. In your configuration, the clients are pointing to name 'A', which is a CNAME resolving to a differnt A-record 'B', which is then resolving to the IP of the Replica 'C'. CNAMES are convenient, particularly for migrations, but are frequently a lazy way to redirect applications and clients following a migration when we either don't want to or don't know how to manually reconfigure the applications and clients properly.
Post #902619
Posted Thursday, September 01, 2011 1:18 AM
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Hi there, the same is my problem. Our application also uses the Computer Name. I don't have an idea about adding the computer name of Mirrored Server in order to make it available to Application Server. Your help shall be appreciated.

P.S. I'd be grateful if you can provide me with descriptive solution.
Post #1168499
Posted Thursday, September 01, 2011 6:28 AM
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praveen.singh (9/1/2011)
Hi there, the same is my problem. Our application also uses the Computer Name. I don't have an idea about adding the computer name of Mirrored Server in order to make it available to Application Server. Your help shall be appreciated.

P.S. I'd be grateful if you can provide me with descriptive solution.


This would depend on how the application is configured to connect to the SQL instance and which network Library the SQl instance is configured to listen for incoming connections. For example, if the SQL instance is using the Named Pipes network library, then this is using NetBIOS. This would require that the Swtich HOst Name method of redirection be used. The Switch host Name will rename the Master server by appending its name with a "-xo". In newer versions of the product (Ca ARCserve RHA), it will rename it with a "-RHA". The Replica server would then be renamed to the name of the master. The Dynamic DNS Flag on the interface (Register This connection with DNS) would then update the Master A-record and assign the IP address of the replica. This way regardless of whether the client or server applications are using NetBIOS or DNS resolution, they would be redirected to the replica.

Switch Host Name would also resolve issues with the Master host name in the system tables being replicated to the replica. The other option would be to use REdirect DNS, then use the commands I listed earlier to set the replica server name. This stored procedure could be included in a User Defined Script to be executed on the replica following a successful switchover.

I hope this clarifies things. Please feel free to let me know if you need clarification.

Best Regards
Post #1168615
Posted Thursday, September 01, 2011 8:12 AM
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Yeah, we've SQL 2008 instance and our application is configured with the computer name.Besides, the computer name is same as the instance name of MSSQL server. So i've a confusion that if I can't give the same computer name for two systems within the same domain and do the mirroring. So your help is still required to me. Hope you are now fully aware of my situation.

Thanks.
Post #1168692
Posted Thursday, September 01, 2011 8:41 AM
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This is an XOsoft (CA ARCserve RHA) specific thread. With that product there are 4 methods of 'Network Traffic Redirection":

1) Redirect DNS: The DNS A-record of the Master is updated with the IP Address of the Replica.

2) Switch Host Name: The Replica is renamed to the hostname of the Master. If teh master is online, then the master is first renamed and the master's host name is appended with either a "-xo" or a "-RHA" (depending on the version). This avoids a duplicate host name contention issue during switchover.

3) Move IP: The IP address of the Master is removed and added to the Replica server. This requires that both the master and replica be on the same subnet.

4) User Defined Scripts: This is a custom redirection method performed by executing scripts written by the customer to customize the switchover and redirection process.

The method or combination of methods used is dependant on the environment and how the client or server applications are configured to connect to the Master server.

If the client and/or server apps are configured to resolve the SQL server name using DNS, then redirect DNS can be used. If you're using NETBIOS resolution, then switch host name can be used. You shouldn't need to change the server name in the system DB's. If this is necessary, then using switch host name would resolve the issue. Otherwise using the stored procedure listed above in a user defined script will be an alternative method to address that issue.

If you could clearly describe the problem or concern you are having specifically with XOsoft (CA ARCserve RHA) I'd be happy to assist further.
Post #1168714
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